Indicating fuse plug



March 23, 1937. KAUFFMAN 2,074,916

INDICATING FUSE PLUG Filed April 24, 1935 Patented Mar. 23, 1937 UNITED STATES PATENT OFFICE IN DICATING FUSE PLUG Application April 24, 1935, Serial No. 18,036

8 Claims.

The present invention relates to circuit breakers used in connection with electrical wiring systems and more particularly to a fuse plug capable, upon the rupture of the fusible element thereof,

6 of giving or emitting visible indication or signal.

The primary object of the invention is to provide an enclosure or casing for the fusible elements of such plugs which can be molded in one piece of insulating material of such a design that the remaining parts of the plug may be easily and readily connected thereto for materially reducing the costs of manufacture thereby rendering the same commercially desirable.

Another equally important object of the inven- 16 tion is to provide a one-piece casing for fuse plugs having properly separated compartments formed therein, one for housing the visible indicator or signal and the other for housing the fusible element whereby when the latter becomes blown or ruptured, the combustible gases given oif are prevented from coming in contact with the indicator or interfere with the successful operation of the same.

A still further object of the invention is to provide a one-piece casing containing a suitable insulating material which can be molded or formed in the ordinary two-piece split mold without using the conventional plungers, thereby materially reducing the cost of making the same.

A still further object of the invention is to provide a one-piece molded casing for fuse plugs which can be formed in a. multiple cavity mold being of such a construction that an insert may be molded jointly within all of the casings within such multiple cavity mold and after the casings are formed, the insert may be readily separated into sections and each section serving as a contact strip for the particular fuse in which it is molded.

Other objects of the invention will be in part obvious and in part pointed out hereinafter.

In order that the invention and its mode of operation may be readily understood by persons 5 skilled in the art, I have in the accompanying illustrative drawing and in the detailed following description based thereon, set out several possible embodiments of the same.

In this drawing:

Figure l is a vertical sectional view through the fuse embodying the present invention;

Figure 2 is a vertical sectional view taken at right angles upon the line 2-2 of Figure 1 in the direction of the arrow points;

5 Figure 3 is a horizontal section taken on the line 3-4 of Figure 1 in the direction of the arrow points;

Figure 4 is a top plan view;

Figure 5 is a horizontal section similar to Figure 3 showing a slightly modified form of the in- 5 vention, and

Figure 6 is a detailed plan view of one of the sections of a two-piece split type mold having the multiple cavities therein from which the fuse casing is formed and having positioned within 10 the mold an insert, which latter serves as a contact for the fuse plug.

Referring now more particularly to the accompanying drawing, wherein like and corresponding parts are designated by similar reference charac- 15 ters throughout the several views, I have herein illustrated a plug fuse comprising a casing molded from a single piece of insulating material. Whereas glass, porcelain or similar plastics having the proper insulating qualities may be em- 0 ployed, I preferably use bakelite or a similar composition. The particular design of this casing is such that it may be molded in an ordinary twopiece mold of the split type without the use of the conventional plungers, thereby not only re-' 25 ducing the cost of the mold but materially reducing the cost of handling the molded casing. In Figure 6 of the drawing, I have illustrated one section of a split type mold that may be employed and this mold having formed therein a plurality of cavities, each indicated by the numeral I. Before placing the bakelite or similar composition within cavities of the mold, I place a metal insert indicated by the numeral 2 within this'section of the mold and extend the same through the vari- 35 ous cavities as shown, so that during the molding operation, this metal insert will be securely embedded in each casing, thereby not only eliminating the complicated and expensive molds for forming the casings of the fuse, but eliminating 40 the subsequent assembling of the metallic insert or contact within each fuse. The casing as formed consists of a central section 3 which acts as a partition for dividing the lamp compartment 4 from the fuse compartment 5. Connected 5 to this central section 3 by means of the diametrically opposite side standards 6 and a central standard I is a base portion 8. The lower or base portion of the casing has a truncated projection 9 forming an annular flange I 0. The cen- 5o tral section 3 has formed with its outer periphery, the screw threads II and adapted to engage these screw threads H is a metallic contact shell l2. The lower annular flange l3 of this shell I! engages the flange Ill of the base portion of the fuse casing and when this shell is so applied, it will completely cover or house the fuse compartment 5. I

The lamp compartment 4 is covered by a domeshaped portion it which is also formed with the casing and has provided therein a sight opening i5 communicating with the opened end l6 of the lamp compartment. The outer edge of the central section 3 of the casing is formed with an annular flange having serrations I! provided in its outer face whereby the operator more easily grips the fuse plug for turning the same into and out of the socket of the cut-out base to which it is to be applied.

The metal insert 2 which is preferably a single sheet of brass, is first bent to the shape as shown in Figure 6 of the drawing and being cut at the points indicated by the numeral IS in order to weaken this brass strip at those points, whereupon it may be broken up into sections and each section which is embedded in a single fuse casing forms a contact strip herein indicated by the numeral l9. This contact strip I9 has one end projecting from the fuse casing and is bent to form a central contact terminal 20 whereas the opposite end 2! of the strip extends within the lamp compartment 4.

The fusible element 22 which is arranged within the fuse compartment 5 has one end connected as at 23 to the contact strip I9 preferably by means of solder and its opposite end extends upwardly between the central section 3 of the casing and the shell l2 so as to form contact therewith.

The indicator as herein shown comprises a glow lamp which may be inserted through the opening l6 and rest within the lamp compartment 4. This glow lamp consists of a glass shell 24 having a diameter slightly less than the interior diameter of the lamp compartment 4 so that when it is placed in position one of the lead-in wires or terminals 25 of the lamp will be held in contact with the upper end 2| of the contact strip without the aid of any additional fastening means. The other leadin wire 26 of the lamp is embedded within a suitable resistor 21 and makes contact through the resistor with the upper end of the shell l2. This resistor 21 is preferably made of a suitable composition placed within the recess formed within the outer periphery of the central section 3 of the fuse casing and forms an additional binding element between the casing and the shell I 2 to prevent the rotation of the latter or the removal of the same from the fuse casing.

In the modified form of the invention as is illustrated in Figure 5 of the drawing, I have shown the central standard I and the opposed side standards 8 as being formed integral with one another thereby providing a fuse compartment 28 which opens to only one side of the fuse casing. This open side of the fuse casing may be covered by a sheet of mica herein indicated by the numeral 29 thereby completely separating the fuse compartment from the contact shell I! and thereby prevent any possibility of short circuit occurring between the contact strip l9, the fusible element 22 and the contact shell l2.

When the fuse 22 becomes blown or ruptured, the combustible gases given of! can readily expand within the fuse compartment for escape to the atmosphere through the opening or vent formed between the screw threads of the shell I2 and the casing.

Whereasany type of indicator now commonly known in this particular art may be employed, I preferably and do use a visible indicator which can be readily detected in dark or lighted places and one which will function even when connected to a broken electrical wiring circuit. This visible indicator is a miniature luminescent gaseous discharge tube containing a rare gas such as neon and argon having arranged therein electrodes, and these electrodes are connected to the lead-in wires 25 and 26. This glow lamp which derives its energy through a capacity effect, not leakage, will operate in an electric circuit having the highest insulating resistance, and in addition, will continue to glow even after the overload or short circuit is removed.

This glow lamp having a circuitstabilizing re sistance in series therewith for not only preventing the passage of excessive currents through the same but being arranged in parallel with the fuse link 22 so that as long as the fuse link remains intact, the current will readily pass therethrough. When a short circuit occurs that causes the fuse link to become blown, the lamp deriving its energy through the capacity effect, will glow, thereby visibly indicating the ruptured condition of the fuse link as long as the circuit remains open, but

upon replacing the fuse link, the current will again flow through the circuit and the resistance element 21 will prevent sumcient energy entering the lamp which would cause the same to remain luminous.

This resistor 21 is preferably arranged externally of the glow lamp and should have a resist ance of approximately 100,000 ohms when used on commercial circuits of 110 volts and consists of ground carbon mixed with glycerine. This composition containing carbon and glycerine when in plastic form is applied within the recess formed within the fuse casing as shown in Figure 1 of the drawing and after so being placed, it is allowed to dry. As the composition dries, it securely adheres itself to the casing as well as the shell [2 and the lead-in terminal 29 of the lamp. The amount of the composition when applied in this manner will vary upon each fuse made but as a resistance varying anywhere between 100,000 and 500,000 ohms is permissible, a great deal of care is not required in the application of this composition to the fuse casing.

The fuse compartments 5 and 28 must each be of sufficient area as to allow the combustible gases given off when the fusible element is blown to expand and must have a vent opening leading therefrom so as to permit the gases to escape. At the same time, the fuse compartment must be sufficiently tight so as to prevent lint or dust collecting about the fuse link and becoming ignited when the fuse is blown. Furthermore, this fuse compartment must be spaced and sealed from the lamp compartment in order to prevent the forces liberating from the blown fuse link coming in contact with the glass bulb of the lamp which would crush the same and thereby render the lamp inoperative. The central section 3 of the fuse casing provides such a separating partition between the lamp and fuse compartments and owing to the threaded connection between the shell 12 and the lamp casing a vent opening is established whereby the combustible gases may be permitted to leave the fuse compartment and yet prevent dust or lint from entering the fuse compartment.

Formed with and projecting from the outer face of the central section 9 and extending at right angles to the lamp housing 4 are the flanges 39. These flanges 30 not only provide a handle or gripping portion for the fuse when applying the latter to its socket of the cut-out base but also provides means whereupon the required markings such as the name of the manufacturer, amperes and volts of the fuse may be applied. Manifestly, the construction herein shown is capable of considerable modification and such modifications as come within the scope of my claims, I consider within the spirit of my invention.

I claim:

1. A fuse plug comprising a casing molded in a single piece of insulating material having a lamp compartment and a fuse compartment formed therein, a central contact strip embedded within said casing providing one terminal for the fuse plug and extending longitudinally through the casing with its intermediate portion exposed in the fuse compartment and its upper end portion extending into the lamp compartment, a l threaded contact shell providing the other terminal for the fuse plug, a fusible link arranged within said fuse compartment and connecting the exposed intermediate portion of the central contact with said threaded contact shell, a glow lamp arranged within said lamp compartment, one terminal of said lamp being connected to the upper end of said central contact extending into the lamp compartment and a resistor connecting the other terminal of said lamp with said threaded contact shell and serving as a bonding element for the shell.

2. A fuse plug comprising a casing molded in a single piece of insulating material having a lamp compartment and a fuse compartment formed therein, a partition formed as an integral part of said casing for completely separating said lamp compartment from said fuse compartment, a center standard extending through the fuse compartment between the partition and the base portion of the casing, a central contact embedded within said casing and extending through the center standard and the partition and base portion of the casing and having its intermediate portion exposed in the fuse compartment and its upper end portion extending into the lamp compartment, said central contact providing one terminal for the fuse plug, a threaded contact shell providing the other terminal for the fuse plug, a fusible element arranged within said fuse compartment and having one end connected to the exposed intermediate portion of the central contact and its other end connected to said threaded contact shell, a glow lamp arranged within said lamp compartment, one terminal of said glow lamp being connected to the upper end of said central contact, said casing having a recess formed therein communicating with the lamp compartment, and a plastic resistance arranged within said recess, and having contact with said threaded shell and serving as a bonding element for the shell the other terminal of said glow lamp being connected to said resistance.

3. A'fuse plug comprising a casing having a central section, a lamp compartment over the central section, a base section, means extending between and formed integral with marginal portions of the said sections for retaining said sections in spaced relation to each other to form a fuse compartment therebetween exposed through the side portion of the plug, a center standard extending between and molded integral with the said sections, a central contact member consisting of a single strip of electrical conducting 75 material having one end portion molded within and projecting from said base section to provide a center contact for the plug, said contact member extending longitudinally through the center standard and having its other end portion extending through the central section and into said lamp compartment, a signal lamp in the lamp compartment having a conductor engaging the last mentioned end of said strip and a second conductor projecting out of the lamp housing at a side of the plug, a threaded contact shell surrounding said sections and a fusible element arranged within said fuse compa tment for connecting said central contact with said contact shell and an initially plastic resistance compound connecting the last mentioned conductor of the lamp with the shell and serving as a bonding means for the shell.

4. A casing for plug fuses consisting of a single piece of molded material providing a base portion, an intermediate portion, spaced side portions molded integral with the base and intermediate portion and holding the intermediate portion in spaced relation to said base portion for providing a fuse compartment therebetween, an outer portion molded integral with said intermediate portion and said outer portion having a horizontally arranged lamp receiving compartment formed therein open at one end and formed with a longitudinally extending sight opening leading from its open end.

5. A casing for plug fuses consisting of a single piece of molded material providing a base portion, an intermediate portion, side portions extending longitudinally of the plug in spaced relation to each other circumferentially of the plug and molded integral with the base portion and intermediate portion and retaining the intermediate portion in spaced relation to said base portion for providing a fuse compartment therebetween, said fuse compartment opening at one side of the casing between the side portions, a projection rising from and molded integral with and extending diametrically across said intermediate portion, said projection being holiow to provide a lamp compartment within said pro- Jection having a sight opening and the intermediate portion being formed with a recess constituting a seat for a resistor and communicating with one end of the lamp compartment.

6. A plug fuse comprising a casing molded in a single piece of insulating material having a base section, an intermediate section, said intermediate section having a fuse compartment formed therein provided with an outlet opening at one side thereof, a lamp compartment formed within the casing and horizontally arranged with respect to said intermediate section, said casing having an opening formed therein communicating with said lamp compartment, is central contact member molded within said casing and extending through said fuse compartment into said lamp compartment, one end of said central contact member projecting from said casing for providing one terminal of the fuse plug, a contact screw shell providing the other terminal of the fuse plug, a fuse link connecting said central contact with said contact screw shell, a partition for closing the outlet opening leading to said fuse compartment, an indicator lamp arranged within said lamp compartment and electrically connected to said central contact, a resistor arranged within the opening communicating with said lamp compartment for electrically connecting said lamp indicator with said contact screw shell.

'7. A combined fuse and fusible element integrity indicator in combination, a casing, center and side contact terminals connected to said casing, a fusible element arranged within said casing and electrically connected to said contact terminals, an indicator having oneterminal electrically connected to the center contact terminal, said casing having a recess formed therein, and an initially plastic resistance compound seated within said recess, said resistance compound electrically connecting the other terminal of said indicator with the side terminal and constituting a bonding element for the side terminal.

8. A combined fuse plug and fusible element integrity indicator comprising in combination a casing, contact terminals connected to said cas- LEROY A. KAUFFMAN. 

